Duane Isely

“Legumes are vital because they provide fixed nitrogen for agricultural soils (the recent substitution of synthetic nitrogen fertilizers certainly being a temporary expedient), and because they furnish most of the protein for human food in high-population parts of the world. Man's dependence on grasses and legumes has been coeval.”

“The seeds of a few kinds of weeds can be carried long distances by natural means; for instance, dandelion seeds are wind-transported, cockleburs and stickseeds are carried by the hair of animals. However, the seeds of most weeds are spread by human agencies, most commonly in mixtures with agricultural seed.”